A laser is a light-amplifying device capable of producing high intensity coherent monochromatic light concentrated in a well-collimated beam, commonly referred to as a laser beam. A typical laser comprises an optical resonator having a laser-active material, i.e., a laser medium, that can be a solid, a liquid or a gas. By operation of the laser, the laser medium's atoms or molecules are excited until they lase, that is, until they emit photons or quanta of light. To excite the atoms or molecules into the lasing state, i.e., pumping, they are subjected to electron or photon bombardment. Upon photon emission, such photons can further trigger other molecules to emit similar photons prematurely and together they form the laser beam. Lasers have a wide variety of uses in such diverse areas as drilling, spectroscopy, welding, cutting, communication, analysis, surgery, and photochemistry.
A laser normally can function only in a small portion of the light spectrum since it is dependent upon the laser medium employed therewith. This is particularly true since the wavelengths emitted by a specific energy transition in a given laser medium is tunable over only a very limited portion of the light spectrum. It is therefore necessary to provide a number of different laser media in order to enable lasers to operate over the entire light spectrum. Many of the laser media available up to now have been solids or gases. However, organic dyes in solution also have been employed and are referred to as "laser dyes". It has been recognized that organic laser dyes in solution can provide advantages not possible with gas or solid laser media. For example, there are several organic laser dyes known that are operable over a relatively broad range of wavelengths. Also, organic laser dyes are capable of being tuned so as to choose a specific wavelength of emission from a range of wavelengths. This is a clear advantage over gaseous or solid laser media which emit at a single wavelength or at very few specific wavelengths. Further, a single laser dye instrument, i.e., a single dye laser, can emit laser beams at widely different wavelengths simply by changing the organic laser dye solution used therewith.
Organic dye lasers and organic laser dyes, however, are not without their shortcomings and disadvantages notwithstanding their known benefits. Some of the problems that are common with known organic laser dyes include poor solubility and steady decline in the power of the laser beam output (whether that beam is continuous or pulsed) as irreversible photodegradation of the organic dyes and/or solvents occurs. Consequently, the useable photochemical "lifetime" or total energy obtained from a given volume of an organic dye in a solvent may be unsatisfactorily short or small.
Notwithstanding the number of known benefits associated with organic laser dyes available today, there is a need to provide new and improved commercially acceptable organic laser dyes that are suitable for lasing. More particularly, there is a need to provide new, improved and more efficient commercially acceptable organic laser dyes that are suitable for lasing especially in the 300-420 nm range as well as other ranges in the light spectrum which are relatively more soluble and relatively more stable photochemically during use so as to provide relatively longer useful lifetimes.